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<p>In this study, density functional theory (DFT) and time-dependent DFT (TD-DFT) are employed to design and investigate pull–push strains of pyrazino[1,2-c] [1,3,2]oxazaborinine chromophores (P1–P5) with a focus on their nonlinear optical (NLO) responses. The UV–Vis spectra reveals distinct absorption features, with P2–P5 exhibiting low-energy transitions in the range of 2.53–2.62 eV (474–490 nm), compared to the higher-energy absorption of P1 at 4.79 eV (259 nm). Oscillator strengths varies significantly, with P3 showing the strongest absorption (f = 0.072). Frontier molecular orbital (FMO) analysis indicates that P2–P5 possess smaller HOMO–LUMO gaps (E<sub>gap</sub>) (0.44–1.42 eV) relative to P1 (5.36 eV), enhancing their electron transfer tendencies. Global reactivity parameters further highlighted the increased softness (<i>σ</i> = 0.35–2.26 eV) and reduced hardness (<i>η</i> = 0.22–1.42 eV) of P2–P5 compared to P1 (σ = 0.19 eV, η = 2.68 eV) tounderscore higher reactivity. Importantly, the first-order hyperpolarizability (<i>β</i><sub><i>0</i></sub>) values of P2–P5 (− 340.62 to − 362.21 a.u.) are markedly larger than that of P1 (− 200.40 a.u.). Dipole moments (µ = 41.68–64.59 a.u.) and polarizabilities (&lt;<i>α</i><sub><i>0</i></sub> &gt; = 221.70–236.15 a.u.) of P2–P5 also exceede those of P1 (µ = 1.19 a.u., &lt;<i>α</i><sub><i>0</i></sub> &gt; = 131.40 a.u.), confirming enhanced charge separation and optical activity. Transition density matrix (TDM), hole–electron overlap, charge density difference (CDD), and noncovalent interaction (NCI) analyses consistently reveals localized donor–acceptor charge transfer (CT) in P2–P5, in contrast to the delocalized transitions in P1. Collectively, these results demonstrate that acceptor-modified pyrazino based derivatives (P2–P5) exhibit superior NLO properties, with large <i>β</i><sub><i>0</i></sub>values, strong dipoles, and efficient CT to make them promising candidates for advanced optoelectronic and photonic applications.</p> Graphical abstract <p></p>

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Designing pull-push strains of pyrazino[1,2-c][1,3,2]oxazaborinine to explore intramolecular charge mediated nonlinear response: a DFT and data driven study

  • 期刊论文

  • 发表日期：

    2026年5月9日

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  • Sadaf Noreen,
  • Mamduh J. Aljaafreh

摘要

In this study, density functional theory (DFT) and time-dependent DFT (TD-DFT) are employed to design and investigate pull–push strains of pyrazino[1,2-c] [1,3,2]oxazaborinine chromophores (P1–P5) with a focus on their nonlinear optical (NLO) responses. The UV–Vis spectra reveals distinct absorption features, with P2–P5 exhibiting low-energy transitions in the range of 2.53–2.62 eV (474–490 nm), compared to the higher-energy absorption of P1 at 4.79 eV (259 nm). Oscillator strengths varies significantly, with P3 showing the strongest absorption (f = 0.072). Frontier molecular orbital (FMO) analysis indicates that P2–P5 possess smaller HOMO–LUMO gaps (Egap) (0.44–1.42 eV) relative to P1 (5.36 eV), enhancing their electron transfer tendencies. Global reactivity parameters further highlighted the increased softness (σ = 0.35–2.26 eV) and reduced hardness (η = 0.22–1.42 eV) of P2–P5 compared to P1 (σ = 0.19 eV, η = 2.68 eV) tounderscore higher reactivity. Importantly, the first-order hyperpolarizability (β0) values of P2–P5 (− 340.62 to − 362.21 a.u.) are markedly larger than that of P1 (− 200.40 a.u.). Dipole moments (µ = 41.68–64.59 a.u.) and polarizabilities (<α0 > = 221.70–236.15 a.u.) of P2–P5 also exceede those of P1 (µ = 1.19 a.u., <α0 > = 131.40 a.u.), confirming enhanced charge separation and optical activity. Transition density matrix (TDM), hole–electron overlap, charge density difference (CDD), and noncovalent interaction (NCI) analyses consistently reveals localized donor–acceptor charge transfer (CT) in P2–P5, in contrast to the delocalized transitions in P1. Collectively, these results demonstrate that acceptor-modified pyrazino based derivatives (P2–P5) exhibit superior NLO properties, with large β0values, strong dipoles, and efficient CT to make them promising candidates for advanced optoelectronic and photonic applications.

Graphical abstract